Immunoradiometric assay of factor VIII: coagulant antigen using four human antibodies. Study of 27 cases of haemophilia A.
Immunoradiometric assay (IRMA) of VIII:C antigen was performed using either IgG or monovalent Fab fragments from four antibodies arisen in polytransfused haemophilia A patients (titre between 100 and 1500 U/ml). Using IgG isolated by a solid or a liquid phase system, only the high titre (greater than or equal to 1000 U/ml) antibodies could be used for IRMA, with a sensitivity of 0.2% VIII:CAg. Using Fab fragments isolated by liquid phase, high and low (less than or equal to 150 U/ml) titre antibodies could be used and the IRMA was significantly improved with a 10-fold higher sensitivity. The affinity of the antibodies for VIII:CAg, studied by displacement curves using a modification of the IRMA, was found not to depend upon the titre of the antibody. Comparative levels of VIII:C and VIII:CAg in 27 cases of haemophilia A emphasize the heterogeneity of this disorder, two types of severe and three types of mild haemophilia being observed.
D000915:Antibody Affinity; D000941:Antigens / Q000032:analysis*; D001777:Blood Coagulation; D004306:Dose-Response Relationship, Immunologic; D005169:Factor VIII / Q000276:immunology*; D006467:Hemophilia A / Q000276:immunology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D011863:Radioimmunoassay / Q000379:methods
D000941:Antigens; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D005169:Factor VIII